We propose to continue our studies on the structure and function of enzymes involved in the regulation of carbohydrate metabolism in relation to hormone action and muscle contraction, with special emphasis on certain evolutionary aspects of these control mechanisms. Specifically, we are interested in: first, the structure of phosphorylase phosphatase, an enzyme that might play a central role in the control of glycogen synthesis and breakdown, and the possible involvement of insulin in its regulation; second, the structure and function of phosphorylase kinase, with particular emphasis on the characterization of its catalytic site and the role of its other subunits, especially one that might be related to actin; third, the structure and amino acid sequence of the catalytic subunit of the cAMP-dependent protein kinase; and fourth, the total structure and physiological function of the heat-stable protein inhibitor of protein kinase that has been recently isolated in this laboratory.